Oven



1,513,161 w. A. DARRAH OVEN Filed March 19, 1920 L :s Sheets-Shet 1 *oct. 28, 1924.

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' W.A.DARRAH OVEN Filed March 19, 1920 3 Sheets-Sheet a I WWQK.

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' Application ifled March 19, 1920. Serial No. 867,298.

To all whom it may concem."

Be it known that I, WILLIAM A. DARRAH, a citizen of the United States, residing at Chicago, in the count of Cook and State of Illinois, have invente a new and useful Improvement in Ovens, of which the following is a specification.

This invention relates to apparatus for baking various materialsand is particularly applicable for the baking of japan, the drying of paint, enamels, and similar purposes including the seasoning of wood or the burningpf oiL from metal or other surfaces.

Other applications of this apparatus will ibe apparent from the description which folows: .1.

It is well known that the baking of japan and allied materials, as wellas the drying of wood and similar" operations, requires a controllable uniform temperaturev together with a continual flow of air or other fluid for removing the vapors given out from materials being dried.

It is further advisable in the drying of paints, japans, and similar substances, to

supply a large portion of the heat in the form of radiant energy, in order to prevent the so-called case hardening or surface drying.

It is obvious in the drying of japans, paints, 'etc., that if the surface is allowed to harden before the volatile solvents are removed, that the resultant finish will be unsatisfactory due to the small pores formed in the hardened surface by the forced passage of the solvent through said surface.

It has been found-that when a considerable portion of the heat is applied. to-the surface in a radiant form, the metal surface becomes warmer than the surrounding air within the oven, and as a result, the solvents are driven off uniformly throughout the thickness of the japan or'paint before the surface has hardened.

One of the objects of this invention, therefore, is to provide anc'ven which will be fuel but still supply a large porheated by of the heat in the radiant form. Referring to the drawings, Figurel is an elevation showing in vertical longitudinal section, one formof oven illustrating this in vention, Figure 2 shows a vertical longitudinal section through the heater, and Figure 3 shows a-vertical cross section of the heater.

Section line BB shows the point' at which the sections given in Figure 4: was taken,

'flues (7) serve to release a no air or fluid, passing through lines (7) allowwhile section lines of Figure 2 shows I the point at which the section shown in Figure 3 was taken. Figured shows a vertical section, taken transversely, thru a typical oven of this kind. Figure 5 is a ducts. .Figure 7 is a section taken on line.

XX of Figure 6. Figure 8 shows partly in section the means for allowing heat to escape fromthe heating ducts into the furnace, to-

gether with one form of operating mechanism. The reference numbers in Figures 5, 6,7 and 8 refer to similar parts to the reference numbers in the other drawings.-

Referring to the drawings, (1) indicates a blower or device for moving a fluid. (2)

indicates a fire box or combustion chamber above which are mounted fluid heaters (3),

through which the fluid or air from blower (1) is passed.

Burners (4) are supplied with fuel and air, and serve to supply the heat to the fire box 2 Pi es (5) conduct air from air heaters (3) to burners (4). Ducts (6) conduct the heated air or 'fiuid from heaters (3) to a series of lines (7 which are indicated as disposed longitudinally along the sides of f the oven.

Valves (8) located along the length of 'on of the ing it to escape into the. oven. Rod (9) aflords a convenient means of controlling valves (8) from the exterior of the oven.

The fines (7) are of varying dimensions, having a smaller surface at one end than at the other in order to radiate difierent' amounts of heat in different portions of the oven.

At the extreme ends of fines (7) ducts (10) are provided connecting with return fines (11) which serve to bring back the air.

or fluid to manifold (12) from which the returnedair or fluid is directed to the blower 1 I v j nlet (13) is provided in manifold design of the oven.

(12) at such a point that additional cold air may be added to the returning air, thus compensating for the amount of air which enters the oven through valves (8).

Vents (14) are provided near the central portion of the oven, connecting with duct (15) which leads the exhaust gases from the oven to'stack' 16).

The oven (1 consists of an elongated chamber and in the cases shown, is provided with inclined vestibules (18) and 20 at the entering and exit ends respectively.

The exact structure of the oven. is not essential to the spirit of this invention, the main essentials being a fairly rigid structure ofmaterials unaffected by heat.

It is desirable to provide heat insulating materials for covering the walls and all surfaces of the oven.

The ovens should also be constructed so that they will be air tight throughout their length. I

In operation, the material to be baked or dried will enter at door (19), pass upward through vestibule (18) and along the length of oven. ('17) leaving by vestibule (20) and door (21).

Air from the blower will pass through the air heaters which are maintained from 800 to 1400 degrees F. The heaters will raise the temperature of the air to about 600 to 700 degrees F., depending on velocity and the The heated air will ass through ducts (6) into heating flues The passage of the heated air through these flues will raise their temperature to from 500 to 600 degrees F., thus making them act as large'radiating surfaces which will thus radiate hea to the-materials to be dried. It will be noted that at the entering vestlbule (18) where the materials are relatively cool, the radiating surface of the flues is far greater than at other portions of the oven. In general .it is desirable to have the radiating surface of the flues taper radually to a minimum value at the exit end of the oven. The objectof the tapering arrangement here described is to provide a radiating surface which is proportional to the heat absorbed by the material passing through the oven. Substantially; the same object may be accomplished by causing the radiating surface of the flues to taper from the central portion of the oven, where they have a minimum value, to the entering end of the oven where they have a maximum value, while in the portion of the oven from the central part to the leaving end the amount of radiating gases may be so reduced that the. heat supplied will merely compensate for radiation and other losses. In this case, the taper of the flue surface is of relatively minor importance. v

. As the materials to be dried enter at 79$ until they reach the stream of circulating air- 7 which enters the oven from valves (8) The air which enters at this point serves to carry off the fumes of the evaporating solvent which, if not removed, are likely to accumulate to a dangerous degree and cause explosions.

The temperature of the, oven may be con.- trolled by means of a thermo-couple (23) inserted in a manifold (24) which connects the air heater with ducts (6). The thermocouple (23) is connected with any standard pyrometer (25) which actuates a relay (26) by means of a battery (27) whenever the temperature rises above the desired value. The relay (26) operates, an electrically .con-

trolled oil valve (27) in fuel line (28) which supplies fuel to burner (4).

One preferred form of this invention consists in having a series of burners supplying heat to combustion chamber (2) and causing the thermo-couple (23) to control the fuel supply of only one burner (4) of the series.

By this system the fuel supply to burner- (4) is either entirely open or entirely closed, depending upon the temperature of the air in manifold (24).

It will be noted that valves (8) are so located as to permit the air from flues (7) to enter the oven after a portion of the heat from. the said air has been given up to the flues and radiated to the material in the oven.

which. the .material to be dried, cooled and travels with the material, thus becoming saturated with vapors of the solvent of the japan and reducing case hardening to a minimum.

By passing the exhaust gases from combustion chamber (2), through stack (16), a permanent draft is established which insures that the circulating air which leaves the oven byconductor ('14), will be positively exhausted. It, is of decided advantage to utilize a positive exhaust of this kind, although I do not wish to restrict this invention to a stack draft, as obviously, a blower or other eriluivalent may be employed.

One of t e advantages resulting from adding the/ cold make-up air to manifold (12) at point (13) consists in reducing the temperature of the air handled by the blower (1).

-It will be evident that the air used as a circulating medium after having absorbed the vapors of the japanned solvent, cannot be re-circulated to advantage without the danger of accumulating considerable amount air which has been used for heating and radiating flues (7) may be returned to the heaters and re-circulated, thus saving a very considerable amount of heat. This feature permits a relatively high economy of the oven which forms the basis of this invention.

Having now fully described this invention what I claim as new and wish to secure by Letters Patent in the United States, is as follows:

1. A heating oven consisting of a chamher, a heating device, a means of moving air through said heating device, closed radiating containers disposed in said oven and heated by the passage of said hot air therethrough,

escape openings connecting to. said closed radiating containers, said radiating containers exposing a graduated radiating surface to the interior of said oven.

2. A heating oven consisting of a firebox,

a source of an under pressure, means for heating said air by said fire box, a radiating container disposed in said even and heated bfi the passage of said air, and means for a owing a portion ofsaid air to escape into' the oven.

3. In a heating oven 5. metal duct presenting a large surface for radiation, said surface arranged to be, greater at the portion of the oven at which the material to be heated enters, and less at the opposite portion.

4. In a heating oven, a radiating duct therein, said duct arranged to conduct hot gases through said oven and to radiate a portion of the heat of said ases to the contents of said oven, the sur ace of said duct being graduated to be greater at the entering portion of said oven and less at the central portion. 1

5. A heating oven consisting of a fire box, a source of an under pressure, means for heating said air by said fire box, a radiating container in said oven, and heated by passage of said air, means for allowing a portion of said air to escape into the oven, and means for positively exhausting the said escaping air. a

6. In a heating oven metal duct of graduated radiating surface arranged to heat said oven by radiation, and means for permitting the escape of a controlled amount of the gases passing through said duct.

7. In a continuous oven, a system of ducts 'for conducting hot gases therethrough, the

radiating surface of said ducts being so pro' portioned that the heat given up by said radiating surface to the materials being heated in the oven, will be a maximum at the entering end and become successively less as the duct passes from the entering end.

8. A heating oven consisting of a chamber, closed radiating containers disposed in said oven, a heatin device, a means of moving air through said heating device without contact with the products of combustion,

connection with said heating device and said closed radiating containers, escape openings connected to said closed radiating containers, 'said radiating containers exposing a graduated radiating surface to the interior of said oven.

.. 9. In a heating device, a multiple of burners supplying heat, a thermostat operated by;

the heat so' supplied, a relay device con-v trolled by said thermostat, a means forcausing said relay device to open or close a part on y of said multiple of burners in order to maintain constant temperature conditions.

10. A heating oven consisting of a chamber, a heating device, a means of moving air through said heating device, closed'radiating containers disposed in said oven and heated by the passage of said hot air there-' tion between said closed radiating containers and said means of moving all.

A. DABRAH. 

